Variations of bar fraction, f_bar, (upper) and distributions of bar size, R_bar, (lower) with stellar mass M_{*, 30 kpc} for galaxies in TNG100 (blue) and TNG50 (red). In the bottom panel, the cyan shaded region represents the 3σ scatter range of bar sizes in the S⁴G survey (Erwin 2018). The black dotted line shows the best-fit relationship between bar size and stellar mass for the S⁴G sample (Erwin 2019). The green dashed lines indicates the 20th percentile of the bar size distribution derived from the S⁴G sample. Galaxies with short bars (bar sizes below the S⁴G 20th percentile) in TNG50 and TNG100 are highlighted with green circles. In the top panel, the solid and dashed lines show the bar fraction for all bars and bars longer than the S⁴G 20th percentile for TNG50 (red) and TNG100 (blue), respectively. The numbers next to the points indicate the number of barred galaxies over the total number of disk galaxies in each stellar mass bin for TNG50 and TNG100. Black line represent the fit of bar fractions observed in the near-infrared S⁴G survey (Erwin 2018).